IDH1 and glioblastoma: In GBM, mutations in classical chromatin remodelers are not as common as in some other tumors, but there are notable exceptions: ATRX (a chromatin remodeler involved in telomere maintenance and deposition of histone H3.3) is mutated in a large fraction of lower-grade gliomas and secondary GBMs with IDH mutation, leading to the ALT (alternative lengthening of telomeres) phenotype (Aguilera and López-Contreras, 2023; Schwartzentruber et al., 2012).